Hydraulic friction clamp coupling for shafts

ABSTRACT

Hydraulically actuatable friction clamp coupling of the type which can be used for clamp connecting a sleeve (2) to a drive shaft (3). The clamp coupling includes a shape deformable inner ring (4) which is adapted to engage the sleeve (2), and which, at the outer surface thereof, is formed as a double, counter directed screw having two screw portions (8, 9) which meet substantially at the longitudinal center of the inner ring (4). The screw flange sides of the screw portions have the shape of saw tooth formed cone surfaces (10) as seen in an axial cross section. The outer rings (5, 6) which, at the inner race thereof, are formed with screw like cone surfaces (11) which are saw tooth shaped in a cross section view, match the cone surfaces (10) of the inner ring (4). The two outer rings (5, 6) form, in common, an intermediate, sealed pressure chamber (14) which is filled with a hydraulic pressure medium adapted to be pressurized from an internal or external source of pressure (7), whereby the outer rings (5, 6) are being pressed apart and the inner ring (4) is being compressed thereby clamping the hollow shaft (2) onto the drive shaft (3). Devices are provided for mechanically blocking the outer rings with full clamp action in their moved-apart conditions.

The present invention generally relates to a friction clamp coupling ofthe type which can be used for clamp connection of a shape deformablesleeve or hollow shaft on a rotatable or axially displacable driveshaft. The invention is more particularly directed to such a frictioncoupling which comprises

an inner ring which can change its shape and which is arranged to engagethe sleeve or the hollow shaft and which, at the outer surface thereof,is formed with cone elements,

at least one outer ring which, at the inner surface thereof, is formedwith cone elements matching the cone elements of the inner ring andwhich is/are adapted to cooperate with said cone elements of the innerring and which, upon an axial displacement of the outer ring in relationto the inner ring, makes said shape-deformable inner ring becomecompressed thereby being pressed against the sleeve or the hollow shaftand being clamped to the drive shaft or the hollow shaft.

Many embodiments of friction couplings of this type are known in theart. For instance the Swedish laid out publication 425,182 (ForenadeFabriksverken) discloses a simple cone coupling apparatus of the saidtype, in which the inner cone sleeve and the outer cone sleeve can bepulled or pressed to an axial mutual displacement and to a clampconnection on a drive shaft by a screw means.

The U.S. Pat. No. 3,596,943 (W F Krauss) discloses a similar conecoupling apparatus comprising three cooperating cone parts which arelikewise displaced in the axial direction in relation to each other by ascrew means for clamp connecting an active part thereof to a driveshaft.

A special type of coupling is known from the Swedish laid outpublication 429,993 (SKF Nova AB), in which the cone elements are splitinto several part elements which, in common, provide a saw-tooth shapedprofile, as seen in an axial cross section. Cone elements designedaccordingly give an improved clamp action, a possibility of controllingthe clamp force in different parts of the friction coupling, and theymake it possible to market the friction coupling with the sleevesthereof as an assembled integral unit. According to said laid outpublication the saw-tooth shaped cone profile can be formed as twocounter-directed threads having thread entries from each end of thesleeve and in which the threads meet at the axial centre of the innercone sleeve. The outer cone sleeve is split into two like outer ringshaving an internal thread profile matching the thread profice of theinner ring, and the outer rings can be screwed onto the inner ring so asto engage each other with their meeting end surfaces. The outer ringscan be pressed apart by a suitable screw means.

All the above mentioned friction clamp couplings of the known type areoperated by some type of screw means. Normally large forces are neededfor safely clamp connecting a machine part on a drive shaft by means ofsaid cone coupling elements, and therefore it is generally necessary touse powerful screw means, and generally it is also necessary to useseveral screw means distributed round the coupling for providing themutual displacement of the inner ring and the outer ring or rings. Itmay also be necessary to make use of inconveniently strong forces fortightening of the screws. It may also be difficult to calculate thetightening force, and thereby also the clamp force, so that said forceis exactly the same for all tightening screws which are distributedround the coupling.

An attempt to solve the problem of obtaining a strong and equallydistributed tightening force is illustrated in the Swedish laid outpublication 448,315 (F Durand). In said publication a hydraulicalpressure medium is used for providing the clamp action. In this case theinner ring is formed as two separate cone rings having the pointed coneends facing each other, and there is also used two outer rings arrangedso that they can be pressed apart actuated by the hydraulic medium. Formaking it possible to mount the two outer rings on the inner ring it is,however, necessary that the cone rings of said inner ring, namedpressure rings, are formed separated from each other, so that they canbe interconnected inside the two outer rings after said outer rings havebeen moved together.

The object of the invention therefore is to solve the problem ofproviding a friction clamp coupling of the initially mentioned typecomprising an inner ring having an even, generally circular, innersurface and an outer surface having a saw-tooth shaped, double andoppositely directed thread profile, and two outer clamp rings, and inwhich the tightening of the coupling, which is made by moving the outerrings apart, is made by a power transmitted by a hydraulic pressuremedium, whereby said power is exactly equally distributed round theentire coupling, and is made with a clamp force which can be varied asdesired from a relatively strong to a very strong clamp force, and inwhich the tightening can be made quickly and simply by means of anexternal source of pressure, and in which the releasing of the clampforce can be made like simply and easily.

Thus, according to the invention the inner ring is of the double,oppositely facing screw type, and the two co-operating outer rings areformed with an intermediate, sealed pressure chamber which can be filledwith a hydraulic pressure medium, which pressure medium can bepressurized from an internal or external source of pressure.

Between the co-operating outer rings there may preferably also be amechanical means for mechanically blocking said outer rings in theirmoved-apart condition. Such a mechanical means may be ring shaped, inparticular semi-annular, segments which can be introduced in the areabetween the moved-apart outer rings, or it may be screw means which arethreaded through one of the outer rings and which block the outer ringsin their moved-apart condition when said screw means is/are tightened.

Further characteristics and advantages of the invention will be evidentfrom the following detailed description, in which reference will be madeto the accompanying drawings.

In the drawings

FIG. 1 shows a first embodiment of a friction clamp coupling accordingto the invention, mainly in an axial cross section view, whichembodiment is suited for clamp connecting a hollow shaft to a driveshaft.

FIG. 2 correspondingly shows a partial axial cross section view of analternative clamp coupling before the hollow shaft is clamped to thedrive shaft, and

FIG. 3 shows the same clamp coupling after it, has been pressurized andclamp connected to the drive shaft.

FIG. 4, 5 and 6 show, in like views, three further alternative frictionclamp couplings according to the invention.

A friction clamp coupling according to the invention can be used forclamp connecting various types of objects, and it is very useful forclamp connecting e.g. a hollow shaft to a drive shaft. The drawingsillustrate this type of application of the invention.

Thus, FIG. 1 shows a friction clamp coupling for clamp connecting ahollow shaft 2 extending from a hub 1 to a drive shaft 3 which can be arotating shaft, an axially displacable shaft or any other type of shaft.

The friction clamp coupling generally comprises an inner clamp ring 4co-operating with two outer rings 5 and 6 which can be moved-apart by ahydraulically actuatable means 7.

The inner clamp ring 4 has a cylindrical inner race which is matchingthe outer dimension of the hollow shaft 2. Exteriorly the inner clampring 4 is, as known in the art, formed as a double screw having twoscrew portions 8 and 9 each having its entry from the end of the innersleeve 4 and meeting at or close to the longitudnal centre of the innersleeve 4. The screw portions 8 and 9 are formed with smooth flank threadsides providing cone surfaces 10 over which the inner ring 4 can beclamped to the hollow shaft 2. The screw portions or threads 8, 9 withtheir cone surfaces 10 provide two profiles which are saw tooth shapedin an axial cross section. The tapering cone surfaces are facing eachother. The flank thread sides or the cone surfaces 10 preferably shouldhave a cone angle which is greater than the friction angle. Said anglemakes the outer rings 5 and 6, when being axially moved-apart, press theinner ring 4 against the hollow shaft 2, and said hollow shaft 2, inturn, is thereby pressed against the drive shaft 3, thereby creating asolid interconnection between the hollow shaft 2, also including the hub1, and the drive shaft 3.

The inner ring 4 can be axially slotted on one or more places, but incase there are relatively narrow tolerances between the inner ring andthe hollow shaft there is no need that the inner ring is slotted, sinceit is still possible to compress said inner ring strongly enough as toprovide a safe clamping of the hollow shaft onto the drive shaft.Similarly the hollow shaft 2 can be axially slotted or non-slotted.

Also, or alternatively the hollow shaft can be slotted in the axialdirection, and the slot thereby have substantially the same length asthe the inner ring.

It is further possible to form the inner ring from several inner ringparts, which can be interconnected by a plastic mounting ring so thatthe multi-piece inner ring appears as an integral unit.

The outer rings are structurally substantially mirror symmetrical withreference to the end surfaces thereof facing each other, and they are,along the inner surfaces thereof, formed with an inner screw part 11corresponding to the screws 8, 9 of the inner ring 4. The outer rings 5,6 can be screwed onto the inner ring 4 from each end thereof, and theyare, in their initial positions, preferably tightened so that the endsurfaces thereof engage each other.

There are at least two sealing rings 12 and 13 between the two outerrings, which sealing rings define an annular chamber 14 therebetweenwhich is to be filled with a hydraulic pressure medium of a type whichis known per se. Via a channel 15, which is filled with a pressuremedium, the chamber 14 communicates with a nipple 16 or a similar meansfor pressurizing the pressure medium. The nipple may be formed for beingconnected to an external source of pressure like an external pressurepump, or it can be a screw having a pressure piston, as shown in FIG. 4,for internal pressurization of the pressure medium in the channel 15 andin the pressure chamber 14 between the outer rings 5 and 6.

The pressure chamber 14 and the sealings between the outer rings can beformed in many various ways, for instance as shown in FIGS. 2 and 3, inwhich one of the outer rings 5' is formed as a piston part 17 and theother outer ring 6' is formed as a cylinder part 18, and in which thesealings 12' and 13' are formed as O-ring sealings on thepiston-cylinder surfaces. FIG. 2 shows the coupling in a non-connected,or not solidly interconnected condition, and FIG. 3 shows the samecoupling in a condition fixedly pressed to the drive shaft 1. It ispossible to exclude the inner sealing 13' and to allow the hydraulicpressure medium to become partly pressed into the area between the conesurfaces 10 and 11 of the outer rings and the inner ring so as tolubricate same thereby facilitating the displacement of the outer ringson the inner ring. A slight leakage of hydraulic fluid during thepressurizing step is acceptable.

In order to block the outer rings 5' and 6' in their moved-apartpositions it is possible to introduce e.g. semi-annularly formed lockingsegments 19 between the rings 5' and 6' , as shown in FIG. 3. After thisis done the pressure of the pressure chamber 14 can be released withoutcausing any problems.

FIG. 4 shows a clamp coupling which is basically of the same type asthat of FIGS. 2 and 3 but in which the external pressure pump issubstituted by a pressure screw 20 which is threaded into the outer ring5' and which is arranged to actuate a pressure piston 21 forpressurization of the hydraulic pressure fluid.

FIG. 5 shows a method of blocking the outer rings in their mounted andmoved-apart conditions. In this case the blocking is made by means ofseveral blocking screws 22 which are threaded axially through one of theouter rings 5'. The object of the blocking screws only is to keep theouter rings safely in their already moved-apart conditions. The screws22, on the contrary, are not dimensioned for being capable of movingsaid rings apart.

FIG. 6 shows an alternative possibility of blocking the outer rings 5'and 6' in their moved-apart conditions. This is done by means of ablocking ring 23 which is threaded on one of the outer rings 6', andwhich by means of sealings 24, 25 define the pressure medium chamber14'. By rotating the blocking ring 23 on its threads it comes toengagement with the other outer ring 5', and the outer rings areaccordingly kept in their moved-apart conditions.

There is a further possibility of securing the outer rings 5 and 6 intheir moved-apart conditions, namely by rotating the rings on theirthreads while the rings are moved-apart, so that said rings, withunchanged clamp force, comes into butt contact with each other. Saidrotation of the rings has to be made at the same time as the hydralicfluid presses the rings apart.

    ______________________________________                                        Reference numerals                                                            ______________________________________                                        1       hub           14       pressure chamber                               2       hollow shaft  15       passageway                                     3       drive shaft   16       pressure nipple                                4       inner clamp ring                                                                            17       piston part                                    5       outer ring    18       cylinder part                                  6       outer ring    19       blocking segment                               7       hydraulic system                                                                            20       pressure screw                                 8       screw part (of 4)                                                                           21       pressure piston                                9       screw part (of 4)                                                                           22       blocking screw                                 10      cone surface (of 5, 6)                                                                      23       blocking ring                                  11      screw part (of 5, 6)                                                                        24       sealing                                        12      sealing ring  25       sealing                                        13      sealing ring                                                          ______________________________________                                    

I claim:
 1. Hydraulically actuatable friction clamp coupling which isused for clamp connecting a shape deformable sleeve to a displaceabledrive shaft comprising:a shape deformable inner ring which is adapted toengage the sleeve radially relative to a longitudinal axis of the driveshaft, said inner ring being a single piece and includinga radiallyouter surface divided into first and second cone surfaces which face oneanother, said first and second cone surfaces when viewed in axial crosssection each including several cone elements such that each of saidfirst and second cone surfaces has a saw-toothed shape in axial crosssection; first and second outer rings mounted on said inner ring,saidfirst and second outer rings having respective inner races provided withrespective third and fourth cone surfaces which face one another, saidthird and fourth cone surfaces when viewed in axial cross section eachincluding several cone elements such that each of said third and fourthcone surfaces has a saw-toothed shape in axial cross section which matchrespectively with the saw-tooth shapes of said first and second conesurfaces, and said first and second outer rings together forming anintermediate, sealed pressure chamber which is filled with a hydraulicpressure medium; and a pressurizing means for pressurizing the pressuremedium in said pressure chamber to press said outer rings longitudinallyapart, such that said third and fourth cone surfaces press inwardlyagainst the matching and cooperating said first and second cone surfacesto cause said inner ring to compress and in turn to compress thedeformable sleeve into frictional engagement with the drive shaft. 2.Friction clamp coupling according to claim 1 and further including amechanical blocking means for mechanically blocking the first and secondouter rings in a moved-apart positions.
 3. Friction clamp couplingaccording to claim 2, wherein the mechanical blocking means is anannular segment introduced between the moved-apart said first and secondouter rings.
 4. Friction clamp coupling as claimed in claim 3, whereinsaid annular segment is formed of two semi-annular elements.
 5. Frictionclamp coupling according to claim 2, wherein the mechanical blockingmeans is one or more screws which are threaded through one of the outerrings and which, when being tightened, are brought to engage the otherone of the outer rings thereby blocking said first and second outerrings in the moved-apart positions.
 6. Friction clamp coupling accordingto claim 2, wherein the mechanical blocking means is a locking ringwhich is threaded onto an outer periphery of one of the outer ringsthereby blocking said first and second outer rings in the moved-apartpositions.
 7. Friction clamp coupling according to claim 2, wherein saidfirst and second cone surfaces are formed on said outer surface of saidinner ring as respective screw portions directed counter to one anotherwhich meet substantially at a longitudinal center of said inner ring;and wherein the mechanical blocking means is formed by the rotation ofone of the outer rings in relation to the inner ring so that the one ofthe outer rings engages the other outer ring at end surfaces facing eachother when said inner ring is fully compressed.
 8. Friction clampcoupling according to claim 1, wherein the inner ring is formed with athrough slot.
 9. Friction clamp coupling according to claim 1, whereinthe inner ring and the sleeve are formed with an axial slot, the slot ofthe sleeve being of substantially the same length as that of the innerring.
 10. Friction clamp coupling as claimed in claim 1, wherein saidfirst and second cone surfaces are formed on said outer surface of saidinner ring as respective screw portions directed counter to one anotherwhich meet substantially at a longitudinal center of said inner ring.